The patient's role in drug therapy is an important and largely overlooked intervening variable in the study of pharmaceutical care and health outcomes. Yet patient decisions with respect to prescription and over-the-counter (OTC) drugs can have profound health outcomes in terms of morbidity and health care utilization. In this study, we propose to examine from a patient's perspective the process and outcomes of arthritis patients' drug regimen decisions. Three primary research questions will be examined: 1) how do patient perceptions about quality of life, symptoms, and medication benefits affect: a) drug regimen adherence (prescribed or recommended) and b) OTC self-care use; 2) what are the effects of patient medication behaviors (adherence and OTC self-care use) on arthritis outcomes including quality of life, clinical symptoms, and health care utilization; 3) how do a patient's perceptions of quality of life vary with their clinical symptoms? Arthritis patients will be enrolled from 2 rheumatology outpatient clinics and followed for 3 years. The sample will include 450 rheumatoid arthritis (RA) patients and 300 osteoarthritis (OA) patients. Individuals will be interviewed by telephone every six months and at clinic visits every 3 months for RA patients and every 6 months for OA patients about their adherence, OTC self-care, beliefs about their medications, somatic experience, quality of life, and out- of-pocket costs of medications. Client calendar diaries will be used to assist interview data collection regarding side effects, health service utilization (hospitalization, emergency room use), purchase of OTC drugs. Pharmacy patient profile records will be collected annually to validate patient reports of medication adherence. Clinical measures of the individual's disease and symptoms will be gathered through Lab and physical measurements. The relationship between their medication behaviors and health related outcomes will be analyzed. Analyses for OA and RA will be done separately because of the differences in disease progression, medication regimen, and functional status over time. The general analysis plan is to test hypotheses derived from the three research questions. Descriptive statistics will be generated for: 1) patterns of adherence to recommended regimens; 2) AIMS scale scores; 3) level of disease activity measures; 4) functional classification; 5) OTC self care; and 6) covariates hypothesized to be important to medication adherence and arthritis outcomes. Continuous dependent variables will be analyzed using multiple regression modelling techniques. Binary and ordinal dependent variables will be analyzed using multiple logistic regression.